This invention relates to the art of ink jet printers and, more particularly, to a reservoir bag for use in an ink delivery system for the continuous refill of disposable ink jet cartridges.
Disposable ink jet cartridges are of course well known and are designed to operate for a useful life during which the head elements will function appropriately a very high percentage of the time during the life of the cartridge. To insure high performance, such cartridges have a predetermined amount of ink contained therein, and the amount of ink in the cartridge is a function of the quantity of printing that the printhead element can do before failing to function at the desired high performance level. When the ink in the cartridge is used up, the cartridge is thrown away. Most often, the printhead of the empty cartridge is still adequately functional and, therefore, it is wasteful to discard the cartridge. Furthermore, frequent replacement of ink jet cartridges is expensive from the standpoint of product usage and is inefficient with respect to the time and energy required of a user making these changes.
Systems have been provided heretofore for refilling ink jet cartridges in order to prolong the life thereof. Such systems have included the manual refilling of cartridges, such as through the use of refill kits, refilling through the use of systems including valves and pumps, as shown in U.S. Pat. No. 4,680,696 to Ebinuma, et al., for example, and continuous ink refill systems such as those shown, for example, in U.S. Pat. No. 4,831,389 to Chan, U.S. Pat. No. 5,159,348 to Dietl, et al., and U.S. Pat. No. 5,469,201 to Erickson, et al., all of which are incorporated herein by reference for background information. In a system of continuous ink supply such as that to which the present invention is directed, ink is continuously supplied to a cartridge from a remotely located ink reservoir bag through flexible tubing between the bag and cartridge. The reservoir bag is located in the printer below the cartridge and ink is drawn into the cartridge from the reservoir bag by a slight vacuum that is created as the ink within the cartridge is depleted. The reservoir bag is positioned below the cartridge to prevent flooding of the cartridge which can occur if the bag is positioned above the cartridge. More particularly in this respect, flooding can occur if the bag is above the cartridge such that the head pressure of the ink in the supply line causes ink to be forced out of the cartridge nozzles. In contrast, if the remote ink supply is positioned too far below the cartridge, the vacuum within the cartridge will not be sufficient to pull the ink into the cartridge from the reservoir bag. This is especially true during the early life of the cartridge and filling system when the continuity of the ink supply is most susceptible to interruption. Such susceptibility to interruption is due to the existence of air bubbles in the reservoir bag and tubing which results from the filling and/or storage process. If these air bubbles are large enough, they can interrupt the siphoning effect which enables the ink to flow upward from the reservoir bag to the cartridge. Accordingly, there is a very narrow operating window for the position of the reservoir bag relative to the cartridge and, since all of the ink in the reservoir bag must fall within the operating window in order for the bag to be depleted of ink, the size of the reservoir bag can be severely limited. Other concerns exist with respect to maximizing the utilization of space for the reservoir bag and maximizing the quantity of the volume of ink therein which is withdrawn from the reservoir bag.